1. Field of the Invention
The invention relates to the manufacture of an anti-fire glazings composed of two sheets of glass maintained separated from one another, between which a layer of an aqueous gel is placed, the aqueous phase of which contains at least one salt in solution and the solid gel phase of which is composed of a polymer.
2. Background of the Prior Art
Anti-fire glazings of this type are known from French Patent FR 2,346,548. During a fire, they work in the following manner: the heat is first absorbed by the water of the aqueous gel. This heat serves to vaporize the water. Then, after vaporization of the water and combustion of the solid organic phase, the salt forms a solid foam crust. This solid foam crust remains, even in the presence of very high heat, and constitutes a heat shield which, moreover, prevents the penetration of heat rays. Using these basic principles, anti-fire glazings have been produced which are flame arresters (Class G of the standard DIN 4102, 5th part dated September 1977) or fire-proof for 90 minutes (F 90 class of fire resistance according to the DIN)
In the known anti-fire glazings indicated above, the polymer component of the solid gelling phase is a cross-linked derivative of polyacrylic acid, for example the polyacrylic acid amide.
During the manufacture of gel anti-fire glazings based on a gelling agent composed of acrylic acid derivatives, monomers of said acrylic acid are used which, due to their toxic nature, have certain disadvantages.
The invention seeks to find, as the gel component, a chemical system which meets all the necessary requirements for an anti-fire glazing of this type, such as, for example, transparency and absence of cloudiness in the gel layer, high salt solubility, and complete solubility of the gelling compound in water where the salt is dissolved, but in which, however, no toxic substance or substance which is a danger to health is used.